Shells (sh/bash/csh/tcsh/ksh/zsh/ etc) read a resource file (somethingrc) when invoked, unless told not to or in certain other situations.
The & is a job control operator, and sends the job into the "background". When it says "[1] 6028" it's telling you that the shell is running your command as its number one background job under PID number 6028. If it returned immediately, most likely it was an error.
If you run the firefox command without the &, then stderror would be directed to your terminal and you'd see what the error might be. Not that it's a big deal, although it might be ... depends on what the error is, of course.
OK, so RH is GNOME and hmm, its SUSE that's KDE out of the box? Technically, GNOME and KDE are "desktop environments", which mean that they are WM's with additional programs and features (or cruft, depending on your slant for that sort of thing). If you like toolbars and icons, helper apps, etc. then it saves you the trouble of finding all those toys yourself ...
It's been a little while since I used GNOME (I'm into XFCE now), but IIRC, it's a matter of right-clicking on the gnome-panel and "adding a launcher" ... much the same as "creating a new shortcut" in that "other" OS ... you'll have to pick an icon and issue a command line, etc. (I don't think the launcher needs the "&") ...
HTH,